The present invention relates to valve seals for valves of internal combustion engines and, more particularly, to a valve seal retainer mechanism.
Internal combustion engines typically have a plurality of reciprocating valves for permitting entry of the combustion mixture into, and exhaust of the combustion products out of, the cylinders. These valves have valve stems which slidably reciprocate within the valve guides bores through the cylinder head of the engine. The valves are actuated in proper sequence by means of rocker arms, push rods, cams and the like, which are well-known in the art.
There typically is provided a bath of oil surrounding the above components to minimize wear during operation of the engine. In particular, it has been found that a certain amount of oil must be allowed to work its way down between the valve stem and valve guides to provide lubrication and prevent excessive wear. However, it is undesirable to permit excessive quantities of oil to work down between the valve stems and guides since the oil will leak into the cylinder causing excessive oil usage by the engine and poor operating characteristics.
Therefore, valve seals are typically provided which meter the amount of oil permitted to pass between the valve stems and the seals. These seals may be stamped from Teflon and are typically positioned around the valve stems immediately above the valve guides. Because Teflon seals cannot be molded to conform to the three-dimensional shape of the end of the valve guides, the flat Teflon seals are held in place by deformable, metallic retaining boots such as those illustrated in U.S. Pat. No. 3,531,134, issued to the present applicant, which secure the seals to the outer wall or shoulder of the valve guides. Such boots are positioned telescopically over the valve guides and deformed to effect frictional engagement therewith.
The engagement between the retaining boots and the outer surface of the valve guides should be tight to withstand the forces exerted by the reciprocating valve stems over a long period of time. It has been found, however, that the retaining boots of the type illustrated in the aforementioned U.S. Pat. No. 3,531,134 may occasionally fail and pull off the valve guide, rendering the seal ineffective.
Because of such potential installation problems, the valve seal retaining boot disclosed in U.S. Pat. No. 3,531,134 has found primary acceptance only in engine rebuilding operations where tolerances are closely controlled. Such boots have not found wide acceptance by engine manufacturers as original equipment because of excessive tolerance problems. This has been the case even though metallic retaining boots of this type, when properly fitted, are superior to other currently available retaining boots.